Marked retrograde and anterograde amnesia of a visual discrimination task in rats with selective lesions of the perirhinal cortex.

Damage to the temporal cortex (TC), the lateral entorhinal cortex (LEC), or their interconnections has disruptive effects on visual memory. The fiber connections between TC and LEC are relayed in the perirhinal cortex (PC) or in the adjacent white matter of PC. PC seems to make up a particularly important structure for mnemonic processing. The purpose of the present study was to examine whether selective PC lesions might affect retroactive or proactive memory, since TC/LEC transections can cause both retrograde and anterograde amnesia. The results show that both PC and TC/LEC lesions impair retroactive memory to similar degrees (Experiment 1). However, PC lesions yielded a slightly stronger impairment of both acquisition and retention in the proactive paradigm than TC/LEC lesions (Experiment 2). These findings give support to the notion that PC plays an important role in formation of memory.